(a) Field of the Invention
The present invention relates to an improvement of the fluid granulating/coating apparatus to be worked by utilizing suction air current.
(B) Description of the Prior Art
For the purpose of granulation and or coating in the manufacture of tablets, pills, etc. of foodstuffs, medical supplies and so forth, the employment of a fluid granulating/coating apparatus such as shown in FIG. 1 has hitherto been popular. This apparatus is so designed that, by virtue of the air current generated by the suction air current generating fan 1 disposed on the top of the apparatus, an air current to stream in the direction of arrows with dotted line is generated within the apparatus, the material accommodated in the fluid storing chamber 2 is whirled up by said air current, and a granulating or coating solvent is sprayed in the atomizing chamber 3 through the nozzle 4 equipped in said chamber 3, thereby making it adhere to the material thus whirled up. This art of effecting granulation by generating a suction air current within the apparatus is admittedly advantageous in the case of application to an apparatus provided with a joint between the respective chambers for facilitating the assembling and demounting thereof as it can prevent the atomized solvent or dust from escaping to the outside of the apparatus. However, conventional apparatuses employing this art have been defective in that, because of the suction air current generating fan 1 being disposed directly above the bag filter 5 for collecting the solvent-deposited material and other dusts, the damper 6 for stopping the air suction work in order to clear off dust attached to the bag filter 5 is also disposed directly above the bag filter 5, and as a result, the safety lid 7 to function as the blast screen for securing the working personnel aganist eventual explosion arising from the relation between the static electricity to be generated by the internal friction of the material per se or the friction between the air current and the material and the inflammable atomized solvent, must be installed by the side of the fan 1 and it is infeasible to provide a sufficiently large-sized safety lid.
Besides, particularly in the medical supplies manufacturing industry, in order to conform to the GMP (good manufacturing practice) regulations, an apparatus of this kind is desirable to be employed on the basis of one unit of apparatus for one kind of material to be granulated or coated. However, in the case of manufacturing varieties of medical supplies, it is extremely difficult to assign one apparatus for manufacturing each item of medical supplies, so that there are many instances where various granulation or coating operations are performed by the use of a single unit of this apparatus. Viewed from this point, the structure of this apparatus permitting demounting of the respective chambers is admittedly convenient as it facilitates the cleaning and repair of the aforesaid chambers, but the disposition of such members as the damper 6 and fan 1 directly above the bag filter 5 would cause adhesion of the dust escaping through the meshes of the filter 5 to these members too. And, inasmuch as it is rather difficult to clean these members perfectly, in the case of this apparatus which is designed to close the damper 6 almost every minute and repeat the motion of clearing off dust attached to the bag filter 5 incessantly by imparting several minutes' oscillation to said filter, there is a great danger of the dust attached to the neglected portions of these members getting mixed in the material in the process of granulation, entailing serious drawbacks from the view point of the control of quality of the products.